It's because the X server doesn't allow another user to connect to it.
Type : 'xhost +' (without quotes) in an xterm when still logged as the user
that started X. Then you will be able to start GUI applications from another
user (root or anybody else, or even from another machine on your network).
This isn't really a big problem, but just more on the annoying side. Whenver I
log in as a regular user, and then open up an xterm, su to root, and then try
to run a GUI application as root, I always get this error:
Xlib: connection to ":0.0" refused by server
Xlib: Client is not authorized to co
